The present invention relates in general to manual override of a brake transmission shift interlock system, and, more specifically, to an electronic override feature that allows the driver to place the vehicle's transmission in an unlocked condition by taking a deliberate action during a brief opportunity when parking the vehicle.
The brake shift interlock (BSI) feature, also known as the brake transmission shift interlock (BTSI), is a commonly used rollaway theft prevention feature that locks the automatic transmission shift lever portion of the transmission range selector mechanism in the park position such that it can be released only when the ignition switch is in the run or start position—thereby requiring an ignition key. As further safety against unintended movement, release of the shifter from the park position also requires depression (i.e., activation) of the vehicle brake pedal. Conventional BTSI systems further require the transmission shift lever to be in the park position before allowing the ignition key to be removed from the ignition switch when securing and vacating the vehicle. Such an interlock is required by regulations in many jurisdictions, such as FMVSS 114 in the United States.
A typical BTSI system utilizes a spring-activated, solenoid-returned locking pin in the range selection mechanism that prevents shift lever movement away from (i.e., out of) the park position. Conventional transmission range positions are identified as PRNDL, including park, reverse, neutral, drive, and low. The BTSI interlock solenoid and locking pin selectably inhibit or enable changes from the park position to the out-of-park positions (i.e., R, N, D, and L). In the event of a failure of the electrical system or a malfunction of the solenoid for releasing the locking pin, an optional, mechanical manual override is permitted by FMVSS 114 and most similar regulations globally, and is usually included by the manufacturer. However, to preserve some of the intended theft prevention attribute and to discourage non-service usage of it by customers, FMVSS 114 and most similar regulations require a manual override design which is only accessible or operable by a tool or a key. Since a “service-only” manual override mechanism is intended to be difficult to access and rarely used, the hardware is usually designed to withstand only infrequent (i.e. low duty-cycle) usage. When accessed frequently or by someone other than trained service personnel, these conventional service manual override mechanisms may be easily damaged.
For economic and complexity management reasons, a vehicle manufacturer typically desires to utilize a single hardware design for a particular vehicle model regardless of the global markets into which that model is sold. However, there are significant regional differences in the needs, associated regulations, and customer behavior associated with some hardware, such as the BTSI system and its mechanical service override. This range of differences extends from jurisdictions that prohibit the inclusion of a mechanical service override to those that require daily usage of the override by many drivers and would prefer BTSI deletion. For example, in some markets in Southeast Asia, rollaway vehicle theft does not often occur. Therefore, no corresponding regulations have been put in place to require a BTSI system. Furthermore, many urban areas in the region are characterized by chronically inadequate space for vehicle parking. In many such places, it has become customary, and often required, to double park vehicles (i.e., in two parallel rows along the edge of a street and in parking structures) while leaving the blocking cars locked with their transmissions out of park (e.g., in neutral), their parking brakes off, and their wheels aligned straight so that drivers of other vehicles can push them out of the way as needed in order to access a blocked parking spot—either when arriving or departing. Such customs evolved easily since most Southeast Asia vehicles included manual transmissions and have no BTSI or other feature to prevent parking in neutral. However, this customer behavior has migrated to drivers of the increasing automatic transmissions market segment in the region. Drivers of automatic transmission vehicles equipped with the standard FMVSS 114 compliant BTSI and mechanical service override have been forced to use this override for their “neutral” parking purposes. This has resulted in problems associated with overuse of the manual override which is intended to only support low duty cycle, service-only use. Further, the designed-in inconvenience of the tool or key access mandated by FMVSS 114 has resulted in customer dissatisfaction with its ergonomics and ease of use.
Some vehicle manufacturers have introduced redesigned mechanical manual override hardware specifically for these markets that is easy enough and durable enough for daily use by drivers. These designs have exposed push-buttons that require no tools to access or actuate, and like the service override, are completely manual and have no brake activation requirement. Even though these designs have been readily accepted by customers as significant improvements to their most important problems, they represent a compromise solution that creates or increases other problems.
Firstly, such high duty cycle mechanical manual override hardware is usually more expensive and increases tooling, engineering, and complexity costs for the vehicle manufacturer. Most importantly, however, by providing uninhibited ease of access, the ability of the BTSI to fulfill its two primary design objectives has been completely compromised; namely, rollaway theft prevention and required brake actuation when shifting from park. Further, these push-buttons are easily accessible by children or front seat passengers of parked vehicles who may not have ready access to the brakes if shifter movement results in vehicle movement.
The present invention overcomes the shortcomings of both types of manual overrides without tradeoffs or compromises in the desirable attributes for any particular jurisdiction and without increases in cost or complexity.